Answer:
Optional
Explanation:
A comma can be defined as punctuation mark that is typically used for indicating a break elements of a series or list in a sentence. Also, it's used to indicate the shortest pause in a sentence.
In English language, a conjunction can be defined as an English word that is typically used for connecting two or more clauses, words, phrases or sentences. Some examples of conjunction are but, and, although, because, or, yet, etc.
When there are three or more items (elements) in a series, the final comma before the conjunction (and, or, nor) is optional.
For example;
a. I came, I saw and I conquered. (No final comma before the conjunction).
b. I came, I saw, and I conquered. (There's a final comma before the conjunction).
c. John swept the floor, made the bed and did some laundry.
d. John swept the floor, made the bed, and did some laundry.
